This application is submitted in specific response to RFA-CA-93-038 entitled "Identification and Evaluation of Tissue Markers for pathological Classification of human Gliomas." Structural abnormalities in the short arm of chromosome 9 (9p) occur frequently in malignant gliomas. It has been suggested that a tumor suppressor gene on chromosome 9p is involved in the initiation or evolution of this neoplasm. The tumor suppressor gene has been localized tentatively to 9p21, within a 1 megabase region that separates the interferon-alpha gene locus and the D9S171 marker. We have cloned new DNA probes that span the 9p deleted region in human gliomas, and have localized the most commonly deleted region to a 50 kilobase fragment. In pilot studies. 7 of 8 glioma cell lines, and 12 of 16 melanoma cell lines, had homozygous deletions of the most informative markers, as detected by PCR analysis. In contrast, previously reported chromosome 9p probes yielded a substantially lower frequency of aberrations. Other studies have shown that 75% of human gliomas lack the enzyme methylthioadenosine (MTA) phosphorylase, because of a breakpoint within the MTAP gene, which is localized at the centromeric end of the deleted region on chromosome 9p21. Based upon these data, the Specific Aims of the proposed experiments are: (1) to complete the characterization of the DNA probes from the commonly deleted region on chromosome 9p in human gliomas, including the putative tumor suppressor gene; (2) to analyze archival and fresh gliomas for homozygosity or hemizygosity at these loci, using a newly developed microtiter format gene dosage assay; (3) to use our existent antibodies against MTA phosphorylase to quantitate levels of the enzyme in extracts of primary gliomas; (4) to correlate the molecular genetic results with the histologic patterns of the gliomas, and with their clinical biology; and (50 to make our new DNA probes, gene dosage assay kits, and tissue specimens available to the cooperating members of the Glioma Marker Network.